We propose to study and describe the sequential morphological changes which are seen in the cells of the mammalian neuroretina during neurogenesis and during prenatal maturation. Part I: The premitotic cells in the ventricular epithelium of neuroretina will be radio-isotope labelled at specified stages of gestation, by in utero injection of 3H-thymidine. The retina of adult animals will be prepared for autoradiographic surviving labeled cells will be described (retinal ganglion cells, amacrine, horizontal, bipolar, and photoreceptor cells) in terms of time of cell "birthday." Part II: We will describe the morphological changes of developing retinal ganglion cells (rgc) as they develop the diverse morphological features of the adult rgc, i.e., large, medium, and small cells. Therefore, populations of rgc's labelled with the isotope at specific stages of neurogenesis will be followed (in successively longer interval post-injection litters) as they undergo morphological changes due to a) cell death, b) growth changes due to increase in size of the eye, c) plastic or inductive effects from developing presynaptic (anterograde) structures or postsynaptic (retrograde) targets of the optic nerve fibres. Part III: The "birthday" of rgc's that project to superior colliculus (SC) and lateral geneiculate nucleus (LGN) will be described by labelling embryos, in utero, with tritiated thymidine as in Part II. The adult animals will then receive injections of Horseradish peroxidase (HRP) in SC or LGN. Development of HRP and the presence of isotope label in the same rgc will describe the time at which the projecting cell was "born."